program Plavnik;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  a, b, i, n:integer;

begin
  readln(n);
  b:=2;
  if (n mod 2=0) then
  begin
    for i:=2 to n div 2 do
      b:=b+2*i;
    writeln(b)
  end else
  begin
    a:=3;
    for i:=2 to n div 2 do
    a:=a+2*i+1;
    writeln(a);
  end;
  readln;



end.
